Abstract/Summary ThehypothesestotestarethatAlu-derivedRNAsviaactivationofdouble-strandedRNA(dsRNA)sensors stimulate production of both anti-inflammatory type 1 IFNs and IL-33 in the absence of stimulation of the pro- inflammatory inflammasome as well as pathways producing TNF-a?. Further, our results argue that tandem repeatsofAluelementswillhavegreateractivitythansingleAluRNAstoactivatetheseresponsesandwillserve astherapeuticcandidates.Ourlong-termgoalwillbetoidentifypotentAludsRNAsthatactivateendogenous dsRNAsensorsanddetermineiftheseAludsRNAsblockandpreventdiseaseprogressioninrodentmodelsof multiplesclerosis,suchasexperimentalautoimmuneencephalomyelitis,andpromoteneuronalre-myelination inrodentmodelsofneuronaldamage.Aluelementsareuniquetoprimatesandabout1,000,000Aluelements existinthehumangenome.AnAluelementisabout300bpinlength,thusAluelementsaccountforabout10% ofthehumangenome,areknowntobetranscribedintoRNAs,andsincetheyarecomposedofhighlyconserved inverted repeats have the potential to form double-stranded structures if transcribed into RNA and stimulate dsRNA sensors. We find that during the relapsing-remitting phase of relapsing-remitting multiple sclerosis (RRMS) there is an elevated type 1 IFN response in peripheral leukocytes that is mediated by dsRNA.This dsRNAfractionislargelycomposedofAluelementsandtheproportionofhighlyexpresseddsRNAAluelements is markedly increased in RRMS patients compared to healthy control (HC). Finally, in vitro transcribed single elementAluRNAwilltriggeratype1IFNresponseatconcentrations~100-foldlessthanthesyntheticdsRNA mimic,polyI/C.WealsoshowthatgenomicpositionsofhighlytranscribedAluelementsarecloseinproximity (<5kb)togenomicpositionsofleukocytetranscriptionalenhancers.Thus,areworkinghypothesisisthatthese Alu containing RNAs that activate type 1 interferon responses are derived from leukocyte enhancers with embeddedAluelements. Besideselevatedtype1IFNresponsesduringtherelapsing-remittingphaseofRRMS,IL-33levelsarealso elevatedandIL33isknowntorequireinterferonregulatoryfactors(IRF)viaaninterferon-stimulatedresponse element(ISRE)foritstranscription.Further,liketype1interferonsandinterferon-responsegenes,polyI/Calso stimulatesexpressionofIL33.ThesedatasupportthenotionthatthesedsRNAAluelementswillalsoinduce IL33expression,whichisrelevanttoourproposalsinceIFN-b?isaproventherapyforRRMS.BothpolyI/Cand IL-33 induce expression of myelin basic protein (MBP) and myelin oligodendrocyte glycoprotein (MOG) and stimulatere-myelinationinademyelinatingrodentmodelofgliotoxicinjury.Totestourhypotheses,wepropose to1)investigatecellularresponsestostimulationbyAludsRNAsand2)evaluateabilityandpotencyofdsRNAs derivedfromsingleAlu,tandemAluandAlu-Linecombinationelementstoactivatetype1IFNresponses.